Adding to Einstein’s quantum world

Almost 80 years after Einstein referred to quantum entanglement as ‘spooky action at a distance’, scientists have found a new form of entanglement involving three particles instead of just two.

Einstein famously disliked quantum entanglement, the idea that there is a special connection between pairs or groups of particles which allows them to influence each other faster than the speed of light, even at distances of billions of miles. Quantum entanglement is one of the central aspects of quantum mechanics, a set of rules that governs the world of the sub-atomic particles.

Researchers at the University of Calgary and the Institute for Quantum Computing in Waterloo, designed an experiment that demonstrated the entanglement of three photons, an elementary particle of light.

"This work opens up a rich area of exploration that combines fundamental questions in quantum mechanics and quantum technologies," says Christoph Simon, co-author of the paper which is published in Nature Physics.

The research builds on a thought experiment published by Albert Einstein, Boris Podolsky, and Nathan Rosen in 1935. Looking at the quantum entanglement between two particles, they tried to demonstrate that quantum mechanics is not sufficient to describe reality. However, seventy-seven years later, the theory of quantum mechanics is still intact, and scientists are still investigating the mysterious process of quantum entanglement.

"It is exciting, after all this time, to be able to finally create, control, and entangle, quantum particles in this new way," says Thomas Jennewein, of the University of Waterloo.

"Using these new states of light it may be possible to interact with and entangle distant quantum computer memories based on exotic atomic gases."

Scientists hope that quantum entanglement could be used in the future for things such as sending secret messages that cannot be intercepted and making computers that function faster than the speed of light.